Extracts of human platelets contain many growth factors. The isolation and characterization of these factors, as well as their interactions, are currently active areas of investigation. The growth factor, TGF-.beta. was originally purified from the acid-ethanol extracts of human platelets (see Assoian. R. K. et al, J. Biol. Chem., 258:7155-7160 (1983)). This method takes advantage of the anomalous chromatographic behavior of TGF-.beta. on a Bio-Gel P60 molecular weight sizing column equilibrated with 1.0M acetic acid (pH 2.7) in the presence or absence of 8.0M urea. That is, TGF-.beta. elutes much later than anticipated when run in 1.0M acetic acid (pH 2.7), but returns to an expected elution volume in the presence of 8.0M urea in 1.0M acetic acid (pH 2.7). This method has also been modified to include a hydrophobic HPLC step using a C.sub.18 resin (Synchropak) (see Derynck, R. et al. Nature, 316:701-705 (1985)). However, these methods are disadvantageous because they are time consuming and produce a low yield.
Cartilage-inducing factor-.beta. (hereinafter "CIF-.beta."), is a factor which is closely related to TGF-.beta. in many respects, e.g., sequence homology and activity (see Seyedin, S. M. et al. Proc. Natl. Acad. Sci., USA, 82:2267-2271 (1985); Seyedin. S. M. et al. J. Biol. Chem., 261:5693-5695 (1987); and Seyedin, S. M. et al. J. Biol. Chem., 262:1946-1949 (1987)). A cation-exchange resin. Whatman CM-52, has been used in the purification of CIF-.beta.. This resin has also been used in the isolation of TGF-.beta. from demineralized bone. A similar cation-exchange resin (i.e.. a CM-Triacryl M resin obtained from LKB) has been used in combination with a Bio-Gel P30 molecular weight sizing column and two HPLC steps, one step using a C.sub.18 resin and the other step using a CN resin, in the purification of TGF-.beta. from bovine kidney (see Roberts, A. B. et al. Biochem., 22:5692-5698 (1983)). However, these methods are disadvantageous because they produce low yields.
Conditioned media also contains many growth factors. The isolation and characterization of these growth factors, as well as their interactions, are also currently active areas of investigation. The growth factor, TGF-.beta. has been purified from conditioned media (see DeLarco, J. E. et al. Proc. Natl. Acad. Sci. USA, 82:5015-5019 (1985). This method involves lyophilizing conditioned media, extracting such with 1.0M acetic acid and carrying out sizing chromatography on the clarified extract on a Bio-Gel P30 molecular weight sizing column. This method is disadvantageous because it is time consuming and produces a low yield.